code: def test_copy():
      ex = datum.xxx * 2 > abs(datum.yyy)
      ex_copy = ex.copy()
      assert ex.to_dict() == ex_copy.to_dict()
  
file_path: altair/tests/expr/test_expr.py
imports: import operator
  import pytest
  from altair import expr
  from altair import datum
  from altair import ExprRef
  from jsonschema.exceptions import ValidationError
label_desc: Use image node_id 8 for calling a global function with example usage: test_copy() without return types